About the origin of Arunachal Pradesh, the earliest citations are found in the prehistoric epics of Mahabharata, Ramayana and other spiritual legends. The historical characters, such as Princess Rukmini, King Bhismaka and Lord Parashuram, were reported to be from the same region. Talking about the substantial evidence, the first ancestors of the tribal groups traveled from Tibet in ancient times, and were soon joined by the Thai-Burmese. Barring the northwestern parts, hardly anything is known about the history of Arunachal Pradesh.
The Ahom chronicles of the 16th century throw some light on the recorded history. Besides, Monpa and Sherdukpen-the tribal, had kept past evidences of the existence of local chiefdoms. As stated by the records, the northwestern parts were swayed by the Monpa kingdom of Monyul that prospered between 500 B.C. and 600 A.D. Later, the northern part of region came partially under the control of Tibet and Bhutan. The Ahom and the Assamese got the control over remaining parts of the state, particularly the ones adjoining Myanmar. They ruled until India was annexed by the British in 1858.
In 1913-14, during the Simla Conference, McMahon Line of 890 km was created as the border linking British India and Tibet. However, the line was not accepted by the Chinese; it was shown as official boundary only in 1937. In 1938, Tawang was shown as a part of Tibet on the map published by the Survey of India. From Dirang Dzong in the west to Walong in the east, the British set their feet in the region in 1944. However, Tibet changed its position on the McMahon Line in 1947 subsequent to the note claiming Tibetan districts to be lying to the south of McMahon Line.
When India got independent in 1947, the situation developed further because People's Republic of China was stern to take over Tibet. Seeing the situation, India announced the McMahon Line to be its boundary in Nov' 1950, and the Tibetans were forced to leave Tawang in 1951. Later in 1954, the NEFA (North East Frontier Agency) was established. The matter was quiet for the next ten years, but again started during the Sino-Indian War of 1962. During the war, the PRC detained most of the NEFA (earlier term for Arunachal Pradesh), and after asserting its victory, it willingly left the McMahon Line.
Consequently, the barter trade with Tibet was terminated. Until 1965, the NEFA was administered by the Ministry of External Affairs, and then by the Ministry of Home Affairs (Governor of Assam). In 1972, it was declared as a Union Territory, and was renamed Arunachal Pradesh. On 20 Feb' 1987, Arunachal Pradesh was constituted as the 24th state of the Indian Union. After so many years, in 2007, the state government has shown green signal to resume barter trade with Tibet. Today, Arunachal Pradesh is a prosperous Indian state where tourism is the major source of revenue generation.